The goal of this project is to develop gene therapy as a potential treatment for HIV-1 infection. In our early work on anti-HIV gene therapy approaches we reported on retroviral vectors designed to express a decoy for binding of HIV to cells (soluble CD4, sCD4). These initial reports revealed two important problems that were in need of resolution. The first observation was that vectors that produce proteins that readily inhibit laboratory strains of HIV-1 (like sCD4) can be ineffective at stopping replication of HIV-1 patient isolates. Our second finding was that gene transfer efficiency into primary lymphocytes was poor (a few %) and needed to be increased. Based on these observations, this project has concentrated on the follow goals: 1. Construct retroviral vectors that effectively inhibit HIV-1 and that could potentially be used in human clinical trials. To do this we produced retroviral vectors containing anti-HIV proteins and/or anti-sense RNAs that specifically target the key HIV-1 regulatory proteins Tat and Rev. In addition, we demonstrated that these vectors can be used to engineer primary CD4+ PBL and that these cells are protected from infection by patient strains of HIV-1. 2. Increase retroviral-mediated gene transfer efficiency into primary PBL. Completion of this aim required, the testing of combinations of physical and biological manipulations designed to increase virus stability and/or cell:virus interaction. This was successfully accomplished and we have further refined the techniques so that they can be scaled-up for potential clinical use. Based on our successfully in vitro studies we are now collaborating on a clinical trial to evaluate these approaches in HIV-1 discordant identical twins. The first patient treatments were initiated in August 1996 and initial data should be available in the Fall of 1996.